While the DMAIC methodology presented below may appear linear and explicitly defined, it should be noted that an iterative approach may be necessary. For instance, you may find that upon analyzing your data (Analyze phase) you did not gather enough data to isolate the root cause of the problem. At this point, you may iterate back to the Measure phase. In addition, prior knowledge of the tools and techniques is necessary in determining which tools are useful in each phase. Remember, the appropriate application of tools becomes more critical for effectiveness than correctness, and you don’t need to use all the tools all the time.